90 Hp Johnson losing prime, stalls after 5-10 minutes at low idle

[Doctrt]

I've been having trouble with my 2000 90hp Johnson outboard. When I bought it, it would barely start, and seemed to not be getting enough fuel. A remote tank proved unsuccessful, so a new fuel pump was put in. This solved about 50% of my issues as it would start and run moderately well although it would stall at any speed after a while. We replaced every tube/line up to the fuel filter and including the fuel filter with no success. It was then that I realized that he was running 50:1 fuel, thinking that the oil injection on the motor wasn't working. Turns out, with all the starting and running that we had done, the oil in the tank was dropping, so it must have been working, resulting in a fuel mixture that was far too rich. I plugged the oil tank and continued to run 50:1 to ensure a proper mix. I then ran sea foam and other cleaners through the motor including a evinrude specific carb cleaner to clean up any excess gunk. Now I've got it running at about 90%. It jumps off the start and really flies (about 70km/hr) at top speed. The only problem that persists is that it stalls at a low idle after about 5-10 minutes. I can usually save it by pumping the ball once or twice, but it is always flat. In fact, before it stalls, I can usually hear what I believe to be the fuel pump ticking as it searches for fuel. I'm at a loss now and searching for answers. Any suggestions? Thanks a mil.

Tim

[jedimaster]

Try having the fuel primer ball and cable hanging vertical with the flow pointing up.

Edited July 19, 2013 by jedimaster

[gburdzin]

Is the fuel line and primer ball in good shape with no air leaks? With the engine not running, if you pump the primer ball until it gets firm, does it stay that way for awhile (10+ mins) or does it go soft pretty quick?

[Freshtrax]

Is the bulb installed in the proper flow direction?

Edited July 19, 2013 by Freshtrax

[aplumma]

You are describing a restriction in the low speed and full throttle circuits of the carb. Carb cleaner are rarely able to clear debris from the passages if it is varnish then it can be dissolved. Once you get to around 20% throttle your midrange circuit feeds in and supplies fuel as needed till the full throttle comes into play. The issues you are having both on the bottom and the top of the carb. circuits indicates the midrange circuit is not getting the help it needs from the metering circuits idle and top end. The rule on carb's are clean them once then clean them again then put them back on the engine. If you are not comfortable tearing down the carb's then take it to a shop there are ports and passages that if enlarged or misunderstood as to how they work can be a waste of your time or damage the carb.

 

Art

[Doctrt]

Is the fuel line and primer ball in good shape with no air leaks? With the engine not running, if you pump the primer ball until it gets firm, does it stay that way for awhile (10+ mins) or does it go soft pretty quick?

We did run a remote tank with working primer bulb and lines with no change so I think we've ruled out anything in front of the carb.

[Doctrt]

You are describing a restriction in the low speed and full throttle circuits of the carb. Carb cleaner are rarely able to clear debris from the passages if it is varnish then it can be dissolved. Once you get to around 20% throttle your midrange circuit feeds in and supplies fuel as needed till the full throttle comes into play. The issues you are having both on the bottom and the top of the carb. circuits indicates the midrange circuit is not getting the help it needs from the metering circuits idle and top end. The rule on carb's are clean them once then clean them again then put them back on the engine. If you are not comfortable tearing down the carb's then take it to a shop there are ports and passages that if enlarged or misunderstood as to how they work can be a waste of your time or damage the carb.

 

Art

Thanks for the response. I'm not exactly understanding the beginning however. I had said that anything above the slightest idle seems fine although the boats speed does gradually slow down at a fast idle. No stalling. I don't find this at full throttle. Everything seems fine, in fact it hums. I do think that ultimately the carb will need to be cleaned and or rebuilt but would debris or varnishing not affect the top end of throttle, as it seems unchanged? Furthermore, would is affect the bulbs ability to stay hard? Would you happen to know anyone in the Whitby area that could do this type of work? Thanks so much for the great responses.

T

[aplumma]

The idle circuit is just a small port that uses a fixed restrictor orifice with the air metered thru a passageway debris will only effect no throttle condition. The movement of the butterfly throat is the addition of air across a pilot jet that interacts with the needle valve. Any restriction of the pilot jet or the needle will allow the fuel/air mixture to change usually leaning it out will stumble on first part of acceleration. The top end is either part of the mid range orifice or a stand alone opening depending on the design. As you open the throttle you create more vacuum and more room between the needle and jet so it is less sensitive to debris. A soft bulb usually indicates either the balls check valve is bad, air leak on hose including the pick up on the tank, or fuel pump not keeping up with the demand. Carbs are different from one design to another and I am speaking in broad strokes here but most engines that run poorly it is the first place to look when issues appear after verifying Spark, Air, and fuel delivery system.

 

 

Art

[sleepjigging]

Do you use 93 octane gas? The stuff from Shell has no Ethanol.

[dhickey]

Have the carb rebuilt by a certified marine mechanic.

[Ainsley]

Are you using a cartridge style fuel filter or an inline style? Depending on the strength of the fuel pump it could be too much restriction.

[DRIFTER_016]

To me this sounds like a vacuum issue.

At idle there is not enough vacuum to operate the fuel pump properly.

I would start off by checking the vacuum line that connects the fuel pump to engine.

If it's OK it could be a leak in another vacuum line somewhere.

It's possible that there is a gasket leak somewhere as well.

 

Could also be a defective fuel pump.

 

Might be worth the $$$ to have your local mechanic diagnose the issue and then you could either fix it yourself or get him to do it.

[danc]

 

 

 

Might be worth the $$$ to have your local mechanic diagnose the issue and then you could either fix it yourself or get him to do it.

Probably the best advice after getting 10 different answers for the same problem.

[Sinker]

This thread is hilarious. We've had every possible fix known to man, but not one person has asked about the fuel line.

 

How old is it? If it was my rig, I'd be replacing the fuel line and primer bulb first. You can't assume anything else until you know that is working, and by the sounds of your description, I'd say your fuel line is toast!!

 

S.

[aplumma]

" A soft bulb usually indicates either the balls check valve is bad, air leak on hose including the pick up on the tank, or fuel pump not keeping up with the demand. "

 

Art

[DRIFTER_016]

This thread is hilarious. We've had every possible fix known to man, but not one person has asked about the fuel line.

 

How old is it? If it was my rig, I'd be replacing the fuel line and primer bulb first. You can't assume anything else until you know that is working, and by the sounds of your description, I'd say your fuel line is toast!!

 

S.

EXACTLY!!!

And that's why the OP said they tried a completely different setup including different hoes and fuel tank and had the same problem, eliminating the line and tank as possible problems.

 

Post #6 of this thread:

We did run a remote tank with working primer bulb and lines with no change so I think we've ruled out anything in front of the carb.

[didoban]

maybe you're idling so low that the engine stalls, raise the idle slightly.

[Doctrt]

maybe you're idling so low that the engine stalls, raise the idle slightly.

 

I've been considering this. I don't however want to troll any faster. Not sure how this will affect my speed. I may need to put on a trolling plate. This still doesn't explain why I'm losing prime at the ball.

 

EXACTLY!!!And that's why the OP said they tried a completely different setup including different hoes and fuel tank and had the same problem, eliminating the line and tank as possible problems. ;)Post #6 of this thread:

 

Exactly. No change.

 

Probably the best advice after getting 10 different answers for the same problem.

 

I would like to take it to someone trustworthy. Anyone in the Durham region?

 

Are you using a cartridge style fuel filter or an inline style? Depending on the strength of the fuel pump it could be too much restriction.

I use an inline filter. I've changed that already thinking that it may have become varnished over. No change.

 

Do you use 93 octane gas? The stuff from Shell has no Ethanol.

I only use Shell's V-power, ethanol free. Can't say what was used before so phase separation and its effects is a definite possibility.

 

 

Thanks for all the great advice. I do think a carb rebuild or at least a good cleaning will do the trick. I'm sure we'll get there eventually and I'll give an update when I do.

T

[Old Ironmaker]

I was tasking to my marine guy the other day when I stopped in to get some 2x4. He and everyone in the area is swamped with repairs. The industry is reporting all types of failures due to phase separation on 10 year old and older 2 strokes. I will be spending the extra money on Esso or Shell 93 octane from here on in.

[bare foot wader]

I have the same model year outboard...I've had zero problems with VRO, I personally think it gets a bad rap for improperly diagnosed issues (I hear the first gen VRO had issues and that opinion seems to have lingered?), but if you want to mix to each their own, as long as you've considered that (aka not mixing in the fuel and oil injection too)

 

my o/b runs like a top but does NOT like to slow idle down to a trolling speed, I don't think any of the older mid range 2 strokes do that well...but it will never stall out on me when just running at idle...I have the carb rebuilt each spring before it hits the water, it likely doesn't need it but doesn't hurt, doesn't cost too much and is peace of mind for me

 

my humble 2 cents worth is you need a carb rebuild and possibly low idle adjusted

[gburdzin]

Just another thought which may be completely useless...but is there a proper way to disable the VRO system on the engine? You mentioned in the original post that you plugged off the oil tank and ran 50:1 mixed gas, but could the VRO pump still be affected the engine in this case? Maybe someone can confirm that plugging the oil tank is the correct way to remove the VRO from the equation.

 

Greg

[beagle dad]

HAD THE SAME ISSUE WITH MINE BY THE SOUNDS OF IT

IN MY CASE GAS TANK VENT WAS PLUGGED

ENGINE STARTED THEN DIED AFTER A LITTLE TANK CREATED A VACUUM RESTRICTING FLOW TILL IT QUIT

TRY RUNNING WITHOUT GAS CAP ON FUEL TANK

[beagle dad]

NO LONGER USE VRO ON MINE..JUST PLUGGED THE LINE HEADING TO ENGINE

[Doctrt]

Hey guys. Boats been in and worked on with no luck thus far. Turned out the plugs were wrong and the mechanic felt I should reconnect the oil injection and run straight gas. He 'cleaned out the fuel system' whatever that means, but to no avail. It continued to stall when idling slowly. After waiting a few days with it in their possession with no work having been done, and no work to be done on it over the weekend, I decided to at least bring it home and have it in the garage over the weekend. So I decided to monkey around with it. I think I may have cracked the code. You guys let me know what you think. It's clearly (to me) that it is a vacuum issue. Fuel is being lost somewhere. I popped the cover off and happened to be pumping the bulb when I noticed gas dribbling/spraying out of the carburator. It could be that thus far, when I was looking at it the motor was fairly level, and not trimmed like I had it today, so I didn't notice this before. I don't think is is normal and my suspicion is that I have either faulty check valves or a float in the carburator that is stuck open. Does this seem likely?

[DRIFTER_016]

If you have a stuck float you will have fouled plugs.

What do your plugs look like after it stalls out?